chapter 3 aviation support equipment

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CHAPTER 3
AVIATION SUPPORT EQUIPMENT
As naval aircraft have become more complex, the equipment used to support them has also become
more complex. The Aviation Machinist’s Mate (AD) uses many different types of support equipment
(SE) to maintain aircraft in optimal condition. Some SE, such as tow tractors and power units, are
common to many different aircraft. There is also a long list of SE that applies only to a specific type or
model of aircraft. Using SE correctly is a challenging, sometimes dangerous, but never routine
operation. The support equipment manuals or the maintenance instruction manuals (MIMs) cover the
proper operating procedures and safety precautions for the use of SE. Read the manuals, learn to
use the equipment, and become qualified on it before you are required to use it.
Over the years, safety procedures and precautions for operating SE have developed mainly from
direct experience. Unfortunately, much of that experience was gained as a result of accidents. Each
of us must be aware that accidents are always present. People cause accidents. We are all capable
of having an accident for any number of reasons. Carelessness, complacency, haste, ignorance,
shortcuts, fatigue, and stress are some of the reasons given for SE accidents. It is amazing, and a
little scary, that the same type of SE accidents happens over and over again each year. Each year,
the Navy spends millions of dollars to repair damaged SE and aircraft caused by the improper use of
SE. Navy personnel are injured, maimed, or killed by improper use of SE because of failure to follow
prescribed safety precautions. We must do something to eliminate these tragedies and costs.
This chapter discusses SE identification and the use of different types of SE. You will learn about the
hazards, safety precautions, and proper procedures to follow when using both powered and nonpowered SE. Finally, you will learn about the SE Training and Licensing Program, as discussed in
Commander Naval Air Forces Instruction (COMNAVAIRFORINST) 4790.2(series).
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Recognize the different types of support equipment.
2. Identify the function of the Support Equipment Training and Licensing Program.
3. Discuss the purpose, operation, and safety precautions in using powered and non-powered
support equipment.
IDENTIFICATION OF SE
In previous years, identifying SE has been somewhat difficult. You learned the designations and
applications of the equipment by association. You knew that an A/S32A-45 was a tow tractor; so were
an A/S32A-31A and an A/S32A-32. There were several more tow tractors, but nothing in their
designations showed that they had anything in common. SE is now undergoing a change in
designations to group them by application. Newly constructed and modified support equipment is now
identified by Military Standard 875A (MIL-STD-875A). This designation system for aeronautical
equipment and support equipment will be identical throughout the military services. Present SE with
old designations remains the same until it undergoes an alteration or modification; then it is
redesigned. Table 3-1 contains all SE code indicators used in the Navy today.
3-1
Table 3-1— Equipment indicator code
INSTALLATION
(1st Indicator)
A. Aircraft or Missile
(Installed in or on
vehicle, non-mission
expendable)
TYPE OF EQUIPMENT
(2nd Indicator)
A. Aircraft or Missile
T. Training
23. Chemical
B. Bombing or Fire
Control or Both (Nonelectronic)
V. Variable Configuration
24. Electrical
C. Air Conditioning
26. Gaseous
D. Detection
27. Hydraulic
E. Destruction
28. Materials. Pliable
(Fabric, rubber, etc.
29. Materials. Rigid
(Metals, Wood, etc.)
32. Mechanical
35. Optical
36. Opti-Mechanical
E. Ground, Not Fixed
38. Invisible Light
(Infrared)
M. Ground, SelfContained (Movable,
includes vehicle but
not self-propelled)
H. Aircraft Loading and
Cargo Handling
K. Aerial Stores
(Munitions)
34. Pneumatic
C. Combination (Ground
and Airborne)
G. Flight Control or
Navigation or Both
(Non-electronic)
J. Indicating
33. Nuclear
F. Ground, Fixed
L. Lubricating
37. Electromechanical
M. Maintenance Aircraft
P. Protection
39. Inertial
42. Electrohydraulic
Q. Reconnaissance (Nonelectronic)
43. Manual
R. Fueling
44. Internal Combustion
S. Personnel
45. Biological
46. Pneumatic-Hydraulic
N. Aircraft or Missile
(Transported, but not
installed in or on
vehicle, non-mission
expendable vehicle)
P. Personal Use (Held or
worn by individual)
S. Ground Self-Propelled
(Include vehicle)
U. Multi-Installation
W. Water
MISCELLANEOUS
IDENTIFICATION
22. Apparel
25. Explosive
B. Aircraft or Missile
(Transported, but not
installed in or on
vehicle, mission
expendable)
PURPOSE
(3rd Indicator)
47. Electro-Pneumatic
T. Testing
48. Hydro-mechanical
U. Special. Not Otherwise
Covered, or
Combination of
Purposes
49. Gunnery
82. Mobile Deployment
(Bare Base) –
Miscellaneous
V. Maintenance
Automotive
83. Mobile Deployment
(Bare Base) Medical Serving
(Including kitchen,
dining, etc.)
W. Graphic Arts
X. Identification
Y. Dissemination
99. Miscellaneous
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TYPES OF SUPPORT EQUIPMENT
SE is all equipment required on the ground to make an aeronautical system, system command and
control system, support system, subsystem, or end item of equipment operational in its intended
environment. SE is primarily that equipment covered by the Aircraft Maintenance and Material
Readiness List (AMMRL) Program. SE is categorized as common general purpose and peculiar
special purpose. SE is normally identified as either powered or non-powered. SE types maybe further
divided into the categories of avionic SE and non-avionic SE. Avionic SE common and peculiar
includes all equipment of an electronics nature used for, but not limited to, the testing,
troubleshooting, alignment, or calibration of aircraft systems or components. Avionic SE includes
general-purpose electronic test equipment (GPETE) and automatic test equipment (ATE). Examples
of this type of SE include multimeters, pressure testers, and fuel quantity indicator test sets. Nonavionic SE common and peculiar includes all equipment that is nonelectric in nature and may be
powered or non-powered. Examples of powered equipment are mobile electric powerplants, aircraft
tow tractors, and mobile air-conditioners. Examples of non-powered SE are engine stands and
maintenance work stands. Table 3-2 shows an example of AS32/A-45 tow tractor designation
breakdown.
Table 3-2 — Equipment type designation
Tow Tractor
Item Name
A
S
32
Aero/Support Ground,
Equipment
SelfPropelled
Mechanical
A
Aircraft or
Missile
Support
45
The 45th
equipment in
the category
to which a
type
designation
has been
assigned
POWERED SUPPORT EQUIPMENT
The most common types of powered SE are tow tractors, mobile electric power plants (MEPPs),
mobile air conditioners, air start units (MSUs), and portable hydraulic power supplies/hydraulic test
stands.
A/S32A-45 Mid-Range Tow Tractor
(MRTT)
The A/S32A-45 Mid-Range Tow Tractor is a landbased, four-cylinder, diesel-powered, three-speed
automatic transmission, liquid-cooled, rear-wheel
drive tractor designed for towing aircraft weighing
up to 80,000 pounds. Standard disk brakes are
provided on the front wheels, and integrated
hydraulic brakes are provided on the rear wheels.
It employs a 12-volt, 800 cold cranking ampere
battery, which supplies power for lights, horn,
starter motor, ignition, and instrumentation. The
mid-range tow tractor is geared to travel at a
maximum speed of 15 miles per hour (mph)
forward and 7 mph in reverse (Figure 3-1).
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Figure 3-1 — A/S32A-45 Mid-Range Tow
Tractor (MRTT).
A/S32A-31A Shipboard Tow Tractor
The Shipboard Tow Tractor (STT) will be required to operate on nuclear powered aircraft carrier
(CVNs) and L-class air-capable ships. The following information includes some of the requirements
for the new STT. The diesel power plant is capable of towing aircraft weighing up to 74,500 pounds
and be capable of 11,200-pound drawbar pull (the force with which the tractor pulls vehicles on the
drawbar behind it) in forward and reverse
directions. It shall engage the aircraft using a
tow bar. The STT will transport and provide
power and fuel to a mounted universal jet
engine start unit (MSU). The STT is no larger
than 70 inches wide, 40 inches high, 121 inches
long, and has a minimum ground clearance of
7½ inches. It operates in ambient temperatures
from -20 to 125 degrees F. It shall be
transportable in military aircraft (C-130, C-17,
and C-5). As required for any typical Navy SE,
the STT is highly reliable, maintainable,
supportable, and capable of meeting
Figure 3-2 — A/S32A-31A Shipboard Tow
environmental, shipboard shock, and vibration
Tractor.
standards (Figure 3-2).
Engine Installation and Removal Vehicle (EIRV)
The purpose of the Engine Installation and Removal Vehicle (EIRV) is to satisfy the operational need
of the Navy and Marine Corps by providing a commercial off the shelf (COTS), mobile,
engine/propeller installation and removal system. This unit has the capability of safely installing and
removing the T56 engine and/or T56 propeller on and from P-3, C-2, E-2, and C-130 aircraft.
Installation and removal of the T56 engine and propeller onto the respective aircraft requires relatively
fine lateral and horizontal adjustments in order to be executed properly. To accomplish this, the Navy
is requiring a commercially available, mobile engine/propeller installation and removal system for
procurement. This project is a valuable use of taxpayer funds because procurement of the system will
reduce damage to the engine/propeller and the airframe, thereby decreasing downtime and
increasing operational readiness. The EIRV was chosen to reduce damage to equipment, reduce
injuries to workers, and increase efficiencies.
MOBILE ELECTRIC POWER PLANTS (MEPPS)
Mobile electric power plants (MEPPs) supply regulated electrical power for aircraft servicing, starting,
maintenance, and testing. There are various types of motor generator assemblies. Some supply
direct current (dc) power only, while others furnish both dc and alternating current (ac) power. The
MEPPs used today are designed for operation on shore stations and aboard aircraft carriers. On
aircraft carriers, these units are usually mobile with minimum vehicular dimensions and weight. They
are designed for the utmost maneuverability and mobility. On shore stations, these units may be
mobile or mounted on trailers that require towing. The type used depends upon the type of aircraft to
requiring service. MEPPs, especially the self-propelled type, are high on the list of SE involved in
ground accidents with aircraft. In addition to the hazards of driving or towing MEPPs with cables still
plugged into the aircraft, there is also the possibility of damage to the aircraft’s electrical or electronic
systems due to improper electrical operation. High voltage is certainly a hazard that should be
considered during the use of all MEPPs. Although insulation and covers provide protection,
malfunctions or improper operation can create electrical shock hazards.
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A/S37A-3 MEPP
The A/S37A-3 Shipboard
MEPP is designed to provide
115-volt ac, three-phase, and
400-Hertz (Hz) or 28-volt dc
electrical power for aircraft
aboard ship (Figure 3-3). The
MEPP is a four-wheeled, selfpropelled vehicle powered by
a three-cylinder diesel engine.
The engine drives the
electrical generator and
hydraulic propulsion system.
A 24-volt dc vehicle electrical
system provides starting,
lighting, and instrumentation.
The variable displacement,
axial piston pump provides
hydraulic pressure to two gear
pumps that drive the rear
wheels. Power steering is
provided to the front axle for
ease of vehicle movement in
congested areas on the flight
deck or hangar bay. The ac/dc
power cables are stored in the
Figure 3-3 — A/S374A-3 MEPP.
compartment near the driver.
One of the primary hazards of this MEPP is the unusual driving characteristic. The rear-wheel
steering puts the maneuvering part of the vehicle behind you. It takes a great deal of practice to
become familiar with rear-wheel steering, and you should be familiar with the equipment before
maneuvering close to aircraft on the flight line.
NC-10C MEPP
The NC-10C is designed for shore-based facilities (Figure 3-4). The unit will supply regulated electric
power up to 90 kilo volt amp (kVA) at 0.08 power factor, 120/208-volt, three-phase, and 400 Hz ac for
servicing, maintenance, and starting of helicopter and jet aircraft. The unit is powered by a Detroit
diesel six-cylinder, two-cycle engine. A portion of the generated ac power is rectified to supply 28-volt
dc at 750 amperes continuously. The unit is self-contained and requires no external electrical or
mechanical sources of power. It may be towed at speeds up to 20 mph. The efficiency of the NC-10C
is not affected on inclines up to 15 degrees maximum in any direction from horizontal. Climatic
conditions of operation are from –18° to 120° degrees (F) or 22° to 50° degrees (C) and under
relative humidity up to 100 percent. It will operate efficiently at altitudes from sea level to 8,000 feet.
The general hazards of high voltage, hot cables, noise, noxious gases, and exhaust heat are all
applicable to the NC-10C. Also the NC-10 does not have lockout circuit to prevent moving the unit
with the cables still plugged into the aircraft.
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Figure 3-4 — NC-10 MEPP.
A/M24M-5 Static Frequency Converter
The Static Frequency Converter (SFC) is a four-wheeled, non-self-propelled vehicle that must be
towed. It is equipped with tie-down rings, pneumatic tires, a mechanical hand brake, and a tow bar for
towing and steering. It is designed for flight deck conditions as well as land-based theaters. The SFC
consists of two major assemblies: the trailer assembly and the converter assembly. Input power is
provided from shipboard and shore-based receptacles that supply an external power source of
440/220 voltage alternating current (VAC), three-phase, 60/50 Hz, ungrounded. The SFC converter
assembly automatically senses either 440 VAC or 220 VAC input. The input phase rotation is
insensitive and will operate normally when rotation is in either direction. The SFC converts the input
power and provides converted power via four 30-foot cables, providing 115 VAC three-phase, 400
Hz, 270 voltage direct current (VDC) and 28 VDC, providing electrical power to aircraft/equipment
aboard ship or shore.
CAUTION
R-22 is nonflammable, nontoxic, non-explosive, and
odorless. However, it can still be dangerous. It can cause
serious “burns” in its liquid state. R-22 vapors displace
oxygen in the air, and if enough is inhaled, it can cause
asphyxiation.
3-6
A/M32C-23 Mobile Air Conditioner
The A/M32C-23 Large Land-Based Air Conditioner (LBAC) is a mobile, four-wheeled, trailer-mounted,
self-contained, six-cylinder diesel-powered unit. This unit contains three 15-ton scroll-type
compressors that provide air-conditioned, dehumidified, or vented ambient air through a standard 8inch ring, collapsible air ducting hose to the aircraft’s electronic equipment or cockpit/cabin areas
during ground maintenance. The LBAC consists of a Generator Engine Set (GENSET) rated at
211kilowatts (Kw), 480 VAC, and 60 Hz at 1,800 revolutions per minute (RPM) with operating controls
for air conditioning and heating systems. The amount of air conditioning can be adjusted at the
control panel. In low speed (30 Hz), a single compressor can output as little as 5 tons of air
conditioning. At high speed (90 Hz), each compressor can output 15 tons for a total of 45 tons of air
conditioning at a discharge temperature between 40 and 65 degrees (F). The tertiary compressor
(COMP-3) is activated first. If additional cooling is required, the secondary compressor (COMP-2) is
activated, followed by the primary compressor (COMP-1). Each-compressor is activated in turn as the
demands for additional cooling increase. The chassis has towing and Ackerman-type steering and
manually operated parking brake. The LBAC is designed for air transport and is provided with tiedown/lifting rings and forklift channels. Some of the hazards for air conditioning units are the same as
other diesel or electrical support equipment. These hazards include noise, high voltage, highpressure fluids, and exhaust fumes. In addition, air conditioners have large, whirling fans and blowers
and refrigerant 22 (R-22) in both the liquid and gaseous state. (Figure 3-5).
Figure 3-5 — A/M32C-23 Mobile Air-Conditioner.
A/M27T-15 Diesel Hydraulic Power Supply (DHPS)
The A/M27T-15 Diesel Hydraulic Power Supply (DHPS) is powered by a four-cylinder, four-cycle
turbocharged diesel engine. During normal operation, the diesel engine operates at 2,100 RPM. The
engine is directly coupled to the main hydraulic pump assembly. The electrical system consists of two
12-volt maintenance-free batteries to power the 24 VDC electrical systems. During initial startup of
the DHPS, battery current energizes the starter motor to crank the diesel engine. During normal
operation, the alternator current is used to power the various lights, controls, cooling fans, and
indicators on the DHPS control panel and keep the batteries fully charged. A warning alarm alerts to a
fault condition before damage to the unit occurs. The DHPS is a four-wheeled vehicle that is not selfpropelled and must be towed or moved manually. It is equipped with tie-down rings, pneumatic tires,
a mechanical hand brake, and a tow bar for towing and steering as shown in Figure 3-6.
3-7
MSU-200NAV
The air start unit is designed to provide
compressed air for main engine start (MES)
and to supply on-board environmental control
system (ECS) with compressed air. The MSU
delivers sufficient bleed air to start the main
engines of all aircraft whose requirements are
within the performance range of the unit. The
MSU comes in two variations. The MSU200NAV Air Start Unit will provide a source of
compressed air for powering Air Turbine
Starters (ATS) and Constant Speed Drive
Systems (CSDS) for aircraft engine starting
and motoring. The MSU-200NAV can be
configured on the Shipboard Tow Tractor
(STT) for shipboard use and mounted to an
A/M32U-16 trailer for shore-based use and
shipboard test cell support (Figure 3-7).
NON-POWERED SUPPORT
EQUIPMENT
Figure 3-6 — T-15 Diesel Hydraulic Power
Supply (DHPS).
So far we have discussed only powered SE.
This portion of the text will discuss nonpowered SE. Non-powered SE is all the
equipment that has no engine or motor
installed to supply power for equipment
operation.
Maintenance Platforms
Maintenance stands, platforms, or work
stands (the names are commonly
interchangeable) give us a means to
reach parts of the aircraft we cannot
safely reach or work on from the
ground. A large variety of types and
models are available. Some of the
stands are common SE used on almost
any type of aircraft; others are very
large stands used only at shore
activities or on one specific type of
aircraft.
Figure 3-7 — Air Start Units (MSU’s).
Most adjustable aircraft maintenance platforms are hydraulically operated. A platform and ladder
assembly is mounted on a caster-equipped base, which enables maintenance personnel to safely
work at heights from 3 feet to a maximum of 20 feet, depending on the stand selected. Because the
design, use, safety precautions, and procedures are generally very similar, we will cover only a few of
the more common stands. Most maintenance work stands become defective through abuse and lack
of care. Most small stands are designed to hold 500 pounds safely. Overloading the stand can cause
some part of the platform structure to bend, causing the lift structure or steps to bind, which in turn
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puts abnormal pressure on the hydraulic cylinder, pump, and lines. Eventually the stand will fail,
either by jamming or collapsing.
B-2 Work Stand
The B-2 Work Stand (Figure 3-8) consists basically of a fixed-height (10-foot) lower structure, a
variable-height upper structure, and a manual pump-actuated hydraulic system for raising and
lowering the upper structure. The upper structure includes a work platform with guardrails and steps
with handrails. The platform and steps, because of parallelogram linkage, stay horizontal throughout
their upward or downward travel. The lower structure includes fixed steps and handrails, a tow bar,
and four free-swivel caster wheels for mobility. Each caster is equipped with a safety locking device
containing a spring-loaded pin, which snaps into notches on the caster pivot axle to lock the caster
swivel. The lower structure also includes four immobilizing jacks with baseplates. The jack plates
press against the ground and act as brakes. You may find some B-2 stands with the foot-lever brakes
(similar to the B-4A and B-5A) instead of the jackscrews. The height range for the B-2 work platform
is from 13 feet to 20 feet. Overall height, including the 3½-foot guardrails, is 16½ feet lowered and
23½ feet raised. The base structure is 10 feet wide and 14 feet long; however, the upper work
platform extends the length of the whole work stand to 21 feet when it is in the lowered position. The
work platform space is 4 feet by 4 feet square. The complete work stand weighs 1,900 pounds. The
hydraulic system on the B-2 includes a hand pump, hydraulic lines, a reservoir, and a hydraulic lift
cylinder with a safety lock. The pump is located on the left-hand angle iron of the platform. Hydraulic
lines lead from the pump to the lift cylinder reservoir, which attaches to the scissor section and
platform structure. The work stand is raised and lowered by using the pump and the release valve the
same as a jack. When the B2 work platform is raised, the
inner barrel of the hydraulic
cylinder is exposed. This
inner barrel has spaced
grooves around it to hold a
safety barrel lock. Most of
the models have a barrel
lock consisting of a ring with
four spring grips, which rides
out on the piston. When the
ring is rotated, cams force
the grips out free of the
barrel. When the ring is
rotated farther, the cams
allow the grips to press
against the barrel and snap
into one of the grooves. The
lock then prevents the
cylinder piston from
collapsing in the event of
hydraulic failure. You may
run across some models that
have a U-shaped bolt
attached to the piston by a
chain. This U-lock is inserted
into a barrel groove to lock
the piston up.
Figure 3-8 — B-2 Maintenance Platform.
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B-4A and B-5A Platforms
The two most common maintenance platforms are
the B-4A and the B-5A (Figures 3-9 and 3-10). Both
work stands are movable, hydraulically operated,
adjustable platforms with ladders. They are
mounted on free-swivel caster wheel assemblies.
Each wheel has a foot-lever actuated mechanical
brake and a swivel lock assembly. The steel-grated
platforms are equipped with safety rails on three
sides, and there are handrails on the ladder. Both
stands are equipped with locking pins that, when
inserted through the top of the platform frame, lock
the scissors. Locking prevents the platform from
collapsing in the event of hydraulic failure. Both
stands are raised by using a hydraulic pump, which
is located on the platform to the left of the ladder.
The stands are lowered by using the hydraulic
release valve on the pump. The major difference
between the B-4A and the B-5A stands is their size
Figure 3-9 — B-4A Maintenance Platform.
and height range. The B-4A extends for a working
height between 3 and 7 feet. The B-5A extends for a
working height between 7 and 12 feet. Both stands have a
capacity of 500 pounds. The B-4A is 8 feet long, 3 feet
wide, and weighs 460 pounds. The B-5A is 8 feet 4 inches
long, 8 feet wide at the base, and weighs 860 pounds.
Other Maintenance Platforms
There are many more types of work stands available to you
from both Navy and commercial sources, from foot-high
work stools to step stools, stepladders, and phase
platforms. These work stands are generally designed for
the specific jobs for which they are used and incorporate
the strength, ruggedness, and features required for safety.
If used properly and with care, they are safe. What is not
safe is anything that was not designed as a ladder or work
stand, such as folding steel chairs, swivel (or even solid)
chairs, boxes, card tables, cans, barrels, drums, tractor
hoods, or the top of any other SE. There are a hundred
other things that people try to use every day instead of
proper work stands. These substitutes are usually available
and convenient, although they are NOT safe. They are
dangerous and cause a tremendous number of falls and
disabling injuries.
ENGINE TRAILERS AND WORK STANDS
Figure 3-10 — B-5A Maintenance
Since the days of the early axial flow turbojet engines, the
Platform.
Navy has moved toward universal engine installation, and
removal, transportation trailers and work stands. These basic trailers and engine work stands are a
matched rail ground-handling system that can be modified to handle different types of engines,
installations, and aircraft by the use of various peculiar support equipment (PSE) adapters and, in
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some cases, hoisting equipment. The equipment in common use today is the engine removal and
positioning trailer, models 4000A and 4000B, and the engine transportation trailer, model 3000B. The
removal and positioning (or installation/removal) trailer, as the name shows, is used to remove and
install engines and move them for short distances. The transportation trailer is used to transport
engines over longer distances and to transfer engines from other trailers or stands using the matched
rail ground-handling system. Actual work on the engine is normally performed after it is transferred to
the engine work stand. The work stand is usually in a fixed location in the hangar or shop.
3000B Trailer
Figure 3-11 shows the 3000B trailer. The unit is a four-wheeled trailer incorporating a detachable,
telescopic tow bar at the front and a tow coupling at the rear. The twin parallel rails are equipped with
male and female quick-disconnect couplings and spring-loaded roller adapter stops on both ends of
each rail. The rails can be mated to the model 4000A or 4000B engine removal stand or the model
3110 engine work stand. The main purpose of the 3000B trailer is to move or transport engines for
short or long distances, such as from hangar to hangar or from squadron to the Aircraft Intermediate
Maintenance Department (AIMD) afloat and Fleet Readiness Centers (FRCs) ashore. The trailer is
one part of the universal matched rail ground-handling system. The trailer weighs 600 pounds and
has a load-carrying capacity of 8,000 pounds. It is equipped with pneumatic tires inflated to 30
pounds per square inch (psi). The rails are 12 feet 8 inches long. The overall trailer is 2 feet 10 inches
high and 6 feet wide.
Figure 3-11 — 3000B Engine Transportation Trailer.
4000A and 4000B Trailers
4000A and 4000B engine removal and installation trailer models are very similar (Figure 3-12). It is a
four-wheeled, mobile, hydraulically controlled, self-supporting unit. The trailer consists of a main
frame supported by four wheels, a lift linkage system, an upper frame holding two cradle assemblies,
and a tube and rail assembly. A detachable, telescopic tow bar provides a means of manually
steering or towing the trailer. Some trailers may be equipped with a tow coupling on the rear.
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The hydraulic system consists of the following:
 Four hydraulic frame lift rams that raise and lower the upper frame assembly (rails)
 Four (two on some models) wheel lift rams that raise and lower the main frame
 Two hand pumps with release valves that operate either the lift rams or the wheel rams
 A two-position selector valve labeled LIFT CYLINDER and WHEEL CYLINDER
 A hydraulic fluid reservoir (two on some models)
 Connecting lines and fittings
Foot-lever actuated drum/shoe types of parking brakes are located on the two rear wheels. Large foot
assemblies, which can be manually lowered, are provided to give the stand maximum stability and
support when required. The tie rods that hold the rear wheels fore and aft and those that control tow
bar steering of the front wheels are configured so that they can easily be disconnected, which permits
all four wheels to be manually positioned for maximum maneuverability in close quarters.
All four wheels are attached to the main frame by hydraulically controlled wheel support arms,
operated by wheel lift rams. A ratchet and pawl system is provided on the rams to safely lock the
rams, mechanically and automatically, as they extend. Pawl handles on each wheel lift cylinder must
be actuated and held to permit the rams to retract.
Figure 3-12 — 4000A Engine Removal/Installation Trailer.
The wheel lift rams permit raising or lowering the main (lower) trailer frame. The main frame can be
lowered right to the deck, provided the four manual foot assemblies are all the way up. The main
frame full up position gives maximum ground clearance and is used when towing or moving the
trailer, particularly when loaded. The forward hydraulic pump and release valve raise and lower the
front end of the main frame. The aft pump and release valve raise and lower the rear end of the main
frame. Operated together, the pumps or release valves raise and lower the whole main frame at
once. The lift linkage consists of four upper and four lower links centrally hinged in a jackknife
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position. The linkage system is raised and lowered by four frame lift rams. These lift rams are also
equipped with a ratchet and pawl system to provide a safe mechanical lock in case of a hydraulic
system leak or failure. Pawl knobs located on all four upper links must be actuated and held to permit
the rams to retract. The upper frame is attached to the lift linkage system and holds a cradle
assembly at each end. Inside each cradle are two rollers upon which the semicircular support tubes,
holding the two parallel rails, can roll (rock from side to side). A rotation adjustment knob, located on
the left side of the forward support tube, permits ±10 degrees of roll adjustment of the rails. Two
traverse adjustment knobs, located on the left side of each cradle assembly, permit ±3 inches of
horizontal lateral (side) movement of the rails. Yaw adjustments up to ±2.25 degrees left or right of
the center line of the rails can be made using just one of the traverse adjustment knobs, or both in
different directions. The 4000A and 4000B trailers should never be used to transport engines, even
for short distances.
3110 Work Stand
The model 3110 Work Stand is a 49-gauge matching rail-type unit designed to mate with rail-type
trailers for the roll transfer of the engine. Model 3110, usually located in the hangar or power plant
work center, allows for the horizontal maintenance and storage of aircraft engines. These stands can
be used on any hard surface and are easily erected and maintained (Figure 3-13).
Figure 3-13 — Model 3110 Work Stand Platform.
3-13
SPECIAL-PURPOSE SUPPORT EQUIPMENT
The Aviation Machinist’s Mate has a
requirement to use special support equipment
to accomplish tasks such as engine removal
and corrosion control activities. The aerobomb hoist and the jet engine corrosion
control cart are examples of this specialpurpose gear.
Hangar Engine Hoists
Hangar engine hoists are used in conjunction
with the air logistic trailer for aircraft engine
removal and installation in some aircraft
(Figure 3-14). Prior to using the engine hoist,
a preoperational inspection, which includes
checking the cable for frayed or broken
strands, must be conducted. Always be sure
that the hoist load test date is current and that
the cable is not damaged.
Figure 3-14 — Hangar Engine Hoist.
WARNING
Never leave an engine unattended while it is being
supported by hoists. Never work or get under an engine
while it is being supported by hoists. When lowering or
raising an engine, do it slowly. Constantly check the engine
clearance with the aircraft nacelle and controls to prevent
damage or binding.
Jet Engine Corrosion Control Cart
The corrosion control cart provides freshwater rinsing or the application of preservation compound to
the compressor section of an engine through a low-pressure spray (Figure 3-15). The primary
components of the unit are a large solution tank, two air cylinders, a work platform with guardrail, four
spray applicator wand assemblies, and the trailer. The 33-gallon solution tank is separated into two
separate compartments. The forward section is a 7-gallon preservative tank. The rear section is a 26gallon freshwater tank. Each tank has its own filler neck and cap. There is a 4-inch opening for water
and a 2-inch opening for the preservative tank. Each tank has a pipe plug at the bottom for draining.
The freshwater and preservative fluid systems each have a shutoff valve, a quick-acting lever valve,
and an applicator wand on/off valve. Two 500-cubic-inches, 3,000 psi air cylinders mount on the left
side of the unit to supply air pressure in order to pump freshwater or preservative from the storage
tanks. Four applicator wands are stored on the right side of the unit. Each wand is about 6 feet long
and attaches to the two 10-foot supply hoses off the storage tanks. A Steel grated work platform on
top of the unit provides a work platform to help operators reach the intakes of helicopter engines.
3-14
Figure 3-15 — Corrosion Control Cart.
WARNING
A drawbar at the front of the trailer provides towing and
steering capabilities. It also incorporates a spring-loaded
“dead-man” brake. If the drawbar is released from the
horizontal towing position, it returns to the vertical position
with considerable force. If a person is unaware of this
feature when disengaging the tow bar from a tractor, there is
the possibility of personnel injury.
SE Training and Licensing Program
The purpose of the SE Training and Licensing Program is to make sure you receive effective training
in the safe and efficient operation of SE on specific types of aircraft. The improper use of SE has
resulted in excessive ground accidents and repair and replacement costs amounting to millions of
dollars each year. It also results in reduced operational readiness. The major reasons for improper
use of SE are lack of effective training and lack of effective supervision. Proper licensing of SE
operators takes the coordinated effort of both the FRC SE division and the user activity.
COMNAVAIRFORINST 4790.2(series) lists the procedures and responsibilities required for the
training and licensing of support equipment operators. The SE Training and Licensing Program
contains two distinct parts. Part one, taught by the supporting FRC, covers the proper operation or
use of the SE. Part two, taught by the user activity, consists of on-the-job training (OJT), practical
exams, and written tests to operate the SE on a specific type/model/series of aircraft. Once this
training is accomplished and documented, the division officer initiates an SE operator’s license and
forwards it for approval.
3-15
End of Chapter 3
Aviation Support Equipment
Review Questions
3-1.
What standard is used to designate new or newly reconditioned support equipment (SE)?
A.
B.
C.
D.
3-2.
Support equipment (SE) is divided into what category or categories
A.
B.
C.
D.
3-3.
64,500
74,500
88,000
100,000
Which type of assistance does the A/M27T-15 provide?
A.
B.
C.
D.
3-6.
A/S32A-45
A/S374A-3
A/S38-3
A/S44B-4
What is the towing weight, in pounds, limitation for the A/S32A-31A Shipboard Tow Tractor
(STT)?
A.
B.
C.
D.
3-5.
Working/Broken
Air/Ground
Common general purpose/Peculiar special purpose
Gravity
Which of the following designator is considered a mid-range tow tractor (MRTT)?
A.
B.
C.
D.
3-4.
MIL-STD-875A
MIL-STD-650
MIL-STD-550
MIL-STD-4790.2
Lifting
Towing
Hydraulic power
Personal transportation
Which of the following pieces of support equipment (SE) is considered non-self-propelled?
A.
B.
C.
D.
A/M24M-5
A/S32A-45
A/S383-45
A/S399-45
3-16
3-7.
What is the height range, in feet, for a B-2 work platform?
A.
B.
C.
D.
3-8.
Which of the following services does a MSU-200NAV provide?
A.
B.
C.
D.
3-9.
1 to 2
5 to 8
8 to 10
13 to 20
Fuel
Main engine start (MES)
Engine water wash
Oil
What is the purpose of a 3000B trailer?
A.
B.
C.
D.
Engine installation
Aircraft towing
Engine repair
Moving or transporting engines for short or long distances
3-10. What is the purpose of a 4000A/4000B trailer?
A.
B.
C.
D.
Moving or transporting engines for short or long distances
Engine repair
Engine installation/removal
Aircraft towing
3-11. Which of the following types of support equipment (SE) is considered special-purpose?
A.
B.
C.
D.
Tow tractor
Hangar engine hoist
Torque wrench
Mobile electric power plant (MEPP)
3-12. What is the main purpose of the SE Training and Licensing Program?
A.
B.
C.
D.
make sure you receive effective training in the safe and efficient operation of SE
support equipment repair training
support equipment inspection training
provide aircraft repair licensing
3-17
RATE TRAINING MANUAL – USER UPDATE
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Pensacola, FL 32508
COMM: (850) 452-9700 Ext. 3102 for the N7 Director.
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3-18